Power tool

Abstract

A power tool includes a housing, a motor, an output spindle, a rotary impact assembly configured to transmit rotational motion with intermittent rotational impacts from a cam shaft to the output spindle, and a transmission.

What is claimed is: 
     
         1 . A power tool comprising:
 a housing having a rearward portion and a forward portion;   a motor disposed in the rearward portion of the housing and having a motor output shaft;   the motor being controlled to run at a speed of at least 15000 rotations per minute (rpm);   an output spindle disposed at least partially in the forward portion of the housing;   a rotary impact assembly disposed in the forward portion of the housing and including a cam shaft, a hammer received over the cam shaft and configured to move rotationally and axially relative to the cam shaft, an anvil coupled to the output spindle, and a spring biasing the hammer axially forward toward the anvil, the rotary impact assembly configured so that the hammer transmits rotational motion to the anvil without rotational impacts when a torque on the output spindle is less than a threshold torque and to apply intermittent rotational impacts to the anvil when the torque on the output spindle is at least the threshold torque;   a transmission configured to transmit rotational motion from the motor output shaft to the cam shaft, the transmission having a gear reduction ratio of at least 14:1;   wherein the power tool is configured to achieve a maximum fastening torque that is at least 1200 ft-lbs, and   wherein a ratio of maximum fastening torque to tool length is at least 5.5 ft-lbs/mm, a ratio of maximum fastening torque to tool housing volume is at least 0.06 ft-lbs/mm2, and a ratio of maximum fastening torque to tool weight, without a battery, is at least 160 ft-lbs/lb.   
     
     
         2 . The power tool of  claim 1 , wherein the power tool is configured to achieve the maximum fastening torque with an input energy of less than 2500 Joules (J). 
     
     
         3 . The power tool of  claim 1 , wherein the power tool is configured to achieve a maximum breakaway torque that is at least 1700 ft-lbs. 
     
     
         4 . The power tool of  claim 1 , wherein at least one of a ratio of maximum tightening torque to transmission diameter of at least 8.0 ft-lbs/mm, a ratio of maximum tightening torque to transmission length of at least 30 ft-lbs/mm, and a ratio of maximum tightening torque to transmission volume of at least 20 ft-lbs/cm2. 
     
     
         5 . The power tool of  claim 1 , wherein a beat rate of the hammer is between 1500 and 2400 beats per minute. 
     
     
         6 . The power tool of  claim 1 , further comprising a battery pack configured to supply power to the motor, the battery pack having a nominal voltage of at least 18 Volts (V) a capacity of at least 5 amp hours (Ah), and an impedance of less than or equal to 50 milliOhms (mOhms). 
     
     
         7 . The power tool of  claim 1 , wherein a diameter of the transmission is between 40 millimeters (mm) and 200 mm. 
     
     
         8 . The power tool of  claim 1 , wherein a length of the transmission is between 15 millimeters (mm) and 60 mm. 
     
     
         9 . The power tool of  claim 1 , wherein the transmission comprises a compound planetary transmission configured to transmit rotational motion from the motor output shaft to the cam shaft, the planetary transmission including a sun gear rotatably driven by the motor output shaft, a planet carrier rotatably driving the cam shaft, a ring gear rotationally fixed relative to the housing, and a compound planet gear, the compound planet gear including a first planet gear meshed with the sun gear but not the ring gear and a second planet gear meshed with the ring gear but not the sun gear. 
     
     
         10 . A power tool comprising:
 a housing having a rearward portion and a forward portion;   a motor disposed in the rearward portion of the housing and having a motor output shaft;   the motor being controlled to run at a speed of at least 15000 rotations per minute (rpm);   an output spindle disposed at least partially in the forward portion of the housing;   a rotary impact assembly disposed in the forward portion of the housing and including a cam shaft, a hammer received over the cam shaft and configured to move rotationally and axially relative to the cam shaft, an anvil coupled to the output spindle, and a spring biasing the hammer axially forward toward the anvil, the rotary impact assembly configured so that the hammer transmits rotational motion to the anvil without rotational impacts when a torque on the output spindle is less than a threshold torque and to apply intermittent rotational impacts to the anvil when the torque on the output spindle is at least the threshold torque;   a transmission configured to transmit rotational motion from the motor output shaft to the cam shaft, the transmission having a gear reduction ratio of at least 14:1;   wherein the power tool is configured to achieve a maximum fastening torque that is at least 1200 ft-lbs, and   wherein a ratio of the maximum fastening torque to transmission diameter is at least 8.0 ft-lbs/mm, a ratio of the maximum fastening torque to transmission length is at least 30 ft-lbs/mm, and a ratio of the maximum fastening torque to transmission volume is at least 20 ft-lbs/cm.   
     
     
         11 . The power tool of  claim 10 , wherein the power tool is configured to achieve a maximum breakaway torque that is at least 1700 ft-lbs. 
     
     
         12 . The power tool of  claim 10 , wherein at least one of a ratio of the maximum fastening torque to tool length is at least 5.5 ft-lbs/mm, a ratio of the maximum fastening torque to tool housing volume is at least 0.06 ft-lbs/mm2, or a ratio of the maximum fastening torque to tool weight, without a battery, is at least 160 ft-lbs/lb. 
     
     
         13 . The power tool of  claim 10 , wherein the power tool is configured to achieve the maximum fastening torque with an input energy of less than 2500 Joules (J). 
     
     
         14 . The power tool of  claim 10 , wherein a beat rate of the hammer is between 1500 and 2400 impacts per minute. 
     
     
         15 . The power tool of  claim 10 , further comprises a battery having a nominal voltage of at least 18 Volts (V), a capacity of at least 5 amp hours (Ah), and an impedance of less than or equal to 50 milliOhms (mOhms). 
     
     
         16 . The power tool of  claim 10 , wherein a diameter of the transmission is between 40 mm and 200 mm. 
     
     
         17 . The power tool of  claim 10 , wherein a length of the transmission is between 15 mm and 60 mm. 
     
     
         18 . The power tool of  claim 10 , wherein the transmission comprises a compound planetary transmission configured to transmit rotational motion from the motor output shaft to the cam shaft, the planetary transmission including a sun gear rotatably driven by the motor output shaft, a planet carrier rotatably driving the cam shaft, a ring gear rotationally fixed relative to the housing, and a compound planet gear, the compound planet gear including a first planet gear meshed with the sun gear but not the ring gear and a second planet gear meshed with the ring gear but not the sun gear. 
     
     
         19 . A power tool comprising:
 a housing having a rearward portion and a forward portion;   a motor disposed in the rearward portion of the housing and having a motor output shaft;   the motor being controlled to run at a speed of at least 15000 rotations per minute (rpm);   an output spindle disposed at least partially in the forward portion of the housing;   a rotary impact assembly disposed in the forward portion of the housing and including a cam shaft, a hammer received over the cam shaft and configured to move rotationally and axially relative to the cam shaft, an anvil coupled to the output spindle, and a spring biasing the hammer axially forward toward the anvil, the rotary impact assembly configured so that the hammer transmits rotational motion to the anvil without rotational impacts when a torque on the output spindle is less than a threshold torque and to apply intermittent rotational impacts to the anvil when the torque on the output spindle is at least the threshold torque;   a single stage compound planetary transmission configured to transmit rotational motion from the motor output shaft to the cam shaft, the transmission having a gear reduction ratio of at least 14:1;   wherein the power tool is configured to achieve a maximum fastening torque that is at least 1200 ft-lbs with a ratio of fastening torque to tool length of at least 135 ft-lbs/inches and a breakaway torque that is at last 1700 ft-lbs with a ratio of breakaway torque to tool length of at least 200 ft-lbs/inch.   
     
     
         20 . The power tool of  claim 19 , wherein a ratio of fastening torque to tool weight without a battery is at least 150 ft-lbs/lb and a ratio of breakaway torque to tool length is at least 215 ft-lbs/lb.